A while back I got the idea of Planet of the Apes as an classic D&D game with "ape as class". Gorillas would be fighters, Orangutan clerics, Chimpanzees magic users, and Humans thieves making each great ape a class.

My question is, what monsters are appropriate for such a setting. Orc, goblins, and other humanoids seem really out of place and missing the point.

7 Answers
7

Oooh, this is a fantastic concept. Don't forget packs of feral humans - especially in the original novel, there were human zoos, where whats-his-face found his captain after being captured.

As an alternative to Mind Flayers, there's also the irradiated humans underground (from Beneath The...) with various psionic powers.

Don't forget that canine and feline species died out, so no wolves or lions or similar. Try mutated crocodiles, or pygmy civilizations (an ape-based kobold analog; just take as many kobold models and templates as you want and simply re-skin them).

Good call on remembering no canine or felines, although I'm not sure how close the rest of this would need to hew to the movies/novels. I basically got it from the idea of ape=class while reading an old Marvel Planet of the Apes comic.
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HerbNAug 25 '10 at 15:01

+1 from me too because I was also thinking that weird looking monkeys, and there are plenty of monkeys that look odd, should replace goblins and kobolds and what not.
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Sheikh JahbootyAug 26 '10 at 0:20

And how would you do that, mechanically?
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PureferretDec 28 '11 at 21:44

With the big cats and wolves and such out of the way, I'd play up the evolution of the other predators that can expand into those niches. Bear, wolverine, and hyena, for example. Even the more fierce prey animals can have evolved into stout opponents, such as wild boar and large stags.

Maybe some of the non-primate creatures have become more highly evolved. Gnolls and lizardmen are good examples of humanoids that might have changed from regular animals. There are probably quite a few bird type humanoids and monsters that would fit into the setting too.

Lycanthropes of various types might also be a direction to explore. If you're human and being driven into extinction being able to assume the form of an animal would be a pretty nice survival mechanism.

In a D&D 3.5 setting, I would go with dire creatures (like dire rats, dire wolfs and dire bears). They are very aggressive and powerful, and fit the evolutionary tendency for creatures to grow in size and physical constitution as time passes.

I'll note that, since you've already deviated from the canonical Planet of the Apes by including wizards, I'm not overly worried about continuity. The absence of canids and felinids will leave a gap; nature abhors an empty niche, and given a few hundred years, other species will fill in those gaps, and a few thousand (1800 or so for the original movies, POTA and Beneath the POTA), it's possible that new species would have evolved.

Demi-human replacements
Gibbons, who are apes, but not great apes, would seem ideal for replacing elves in such a setting. Different enough to be way out there. Alternatively, mystic-acrobat would fit, as well...

Monkeys likewise could be used to fill in the demi-humans' roles, should you opt for that.

D&D tends to treat orcs as the "cheap kill" experience fodder, and thus has them breeding much like rabbits. Since they breed like rabbits, why not replace them with rabbits. Some rabbits can get impressive in size - up to several kg in domestic breeds. Really, they would be a better fit for the smaler goblins and kobolds.

Other Critters
Most any natural animal from Cyclopedia, AC9 Creature Compendium, or the AD&D monster manuals, aside from the extinct predators (canids and felinids), work well.

ROUS (Rodents of unusual size) and Weasels will likely fill the wolf niche of hijacker and harrier in North American settings; Badgers, too, will expand their range of prey.

Horses and deer make for great potential monsters. Real world, horses and deer have been known to eat meat in the wild. (cite 1 horses, cite 2 deer) So, having a speciation event where they go back to eating meat isn't untoward. Also, note that precursor horses were omnivores... and some horses still to date grow canines and premolars as a genetic throwback.

Terror Birds, in the absence of industrialized populations, are likely to rehappen, too. Take an eagle or raven, and have them grow huge. Geese and swans are already dangerous. Now, think a raven or crow in the 50-80 pound range, 15' wingspan, smart, greedy, and mean.

Bears are a likely source for megafauna predators.

There are lots of snakes and lizards in North America.

And that's all before any magic stuff.

And so we add magic and radiation
Adding magic, and the radiation from the wars implied by the nature of the changes in the physical environment...

Giant bugs (Keep it reasonable, and you limit them to a couple feet long; adding magic, 8'long roaches).

Land crabs that get huge. Crayfish that decide land flesh is good. 60' Crocodilians and snakes.

Possibly even escaped dinosaurs, recreated by mad scientists just before the ape-takeover.